The present invention relates to a heavy duty pneumatic tire having a block pattern, and more particularly a heavy duty pneumatic tire capable of suppressing railway wear and reducing heel-and-toe wear.
A heavy duty pneumatic tire employs a block pattern having a plurality of block rows in a tread surface composed of a plurality of main grooves extending in a tire circumferential direction and a number of lateral grooves intersecting these main grooves. It is known that in the heavy duty pneumatic tire having such a block pattern, an increase in a running distance produces uneven wear called heel-and-toe wear in which a trailing edge wear of each block of block rows arranged in the center side of a rib or a block of a shoulder area is greater than its leading edge wear. Also, uneven wear called railway wear may occur, in which the outer portion of each block in a tire width direction, arranged inside the shoulder area, is unevenly worn away.
For countermeasures to prevent the foregoing railway wear, for example, as is disclosed in Japanese patent application Kokai publication No. 8-72508, a narrow block is provided in a position outside each block being composed of the block rows inside of the shoulder area in a tire width direction with interposing a sub groove. This countermeasure has been effective for reducing railway wear, but has proven to be ineffective for reducing heel-and-toe wear.